European Urology

Shai I, Schwarzfuchs D, Henkin Y, Shahar DR, Witkow S, Greenberg I, Golan R, Fraser D, Bolotin A, Vardi H, Tangi-Rozental O, Zuk-Ramot R, Sarusi B, Brickner D, Schwartz Z, Sheiner E, Marko R, Katorza E, Thiery J, Fiedler GM, Blüher M, Stumvoll M, Stampfer MJ. Dietary Intervention Randomized Controlled Trial (DIRECT) Group
N Engl J Med 2008;359:229–41
Expert’s summary:
This prospective, randomized, controlled intervention assessed three different diets for weight loss among 322 people in Israel who were either overweight or had diabetes or coronary artery disease (CAD). Eighty-six percent of subjects were men. Subjects were randomized to a low-carbohydrate (<20 g/day slowly titrated up to 120 g/day with no caloric restrictions), Mediterranean (moderate fat, restricted calorie with fat predominantly from olive oil and nuts), or low-fat diet (low calorie, 30% dietary fat) for 2 yr. All subjects were enrolled from the same workplace and ate lunch (the predominant meal in Israel) at the workplace cafeteria, with food provided by the investigators labeled with calorie and macronutrient content and color coded as to whether subjects in each group should “feel free to consume” or “consume in moderation,” although subjects could eat what they wanted. Compliance was high at 24 mo, with the low-fat group consuming 30.0% dietary fat and 572 fewer kcals than at baseline, the Mediterranean diet significantly increasing monounsaturated-to-saturated fat ratios and reducing kcal intake by 372 kcal, and the low-carbohydrate group reducing carbohydrate intake from 51% to 40% and cutting kcals by 550 from baseline.

All groups lost weight. At 6 mo, weight loss was greatest in the low-carbohydrate group, with the Mediterranean and low-fat diet groups having similar weight loss. After 6 mo, the low-carbohydrate and low-fat groups gained weight, and by 24 mo, the greatest weight loss was in the low-carbohydrate (4.7 kg) and Mediterranean groups (4.4 kg), with less weight loss in the low-fat group (2.9 kg). The low-carbohydrate group had the best improvements in cholesterol-to-high–density lipoprotein (HDL) levels, and the low-fat group had the fewest improvements in cholesterol levels.
Experts’ comments:
The adverse consequences of obesity are well established, including CAD, diabetes, arthritis, erectile dysfunction (ED), and cancer. For urologic cancers, obesity increases the risk of death from prostate and kidney cancer [1]. The benefits of weight loss on cardiovascular health are clear. What is less clear is (1) whether weight loss improves cancer outcomes and (2) what weight loss diet is best. Regarding the first point, in animals, caloric restriction (ie, weight loss) slows cancer growth [2]. Whether similar effects occur in humans is unclear, although weight loss is unlikely to be harmful for early-stage prostate or kidney cancer patients. Regarding the second question, this article helps shed some light on this issue.

This article, coupled with other, recent studies [3], [4], and [5], suggests that the degree of weight loss obtained and the health benefits of a low-carbohydrate diet may be greater than low-fat dietary interventions. Moreover, despite similar weight loss, the cholesterol changes appeared to be better than in a Mediterranean diet. Thus, even though there is concern about adverse cardiac and lipid effects of a high-fat, low-carbohydrate diet, the scientific data to date suggest no increased risk of cardiac effects and greater improvements in lipid profiles with 2-yr outcomes. Finally, although low-fat diets slow prostate cancer (PCa) growth in mice independent of weight loss [6] and [7], low-carbohydrate diets appear to slow experimental PCa growth as much as low-fat diets [8] and [9]. Are these data strong enough to recommend low-carbohydrate diets to our overweight cancer patients?

Obesity is a major problem in the United States and is a rapidly growing problem in Europe. Given the cardiovascular benefits of weight loss, we believe it is reasonable for the urologist to council all overweight or obese patients to lose weight. For cancer patients, there appears to be a “teachable” moment shortly after diagnosis of cancer when patients are most receptive to lifestyle changes [10]. As such, we believe it is helpful when counseling cancer patients about nutrition and lifestyle to encourage weight loss. Although not specifically examined in this study, certainly regular exercise is an important part of that advice. Regarding the best dietary approach, this study suggests one “might consider more than one dietary approach, according to individual preferences and metabolic needs, as long as the effort is sustained.” If patients are able to count calories and reduce daily caloric intake, then a low-fat or Mediterranean diet are reasonable options. However, cutting carbohydrates without specifically controlling meal portions also appears to be a reasonable and potentially more effective approach. In our opinion, the urologist may potentially play an extremely important role in patients’ diet and lifestyle decisions. In our experience, patients really do listen to what we suggest, and we have seen numerous patients drastically reducing their weight and improving their diet and exercise levels purely based on our suggestions. We feel the urologist should recommend weight loss to overweight patients and offer patients a referral to a nutritionist if they so desire. To do otherwise is a disservice to our patients.

Conflict of interest

The authors have nothing to disclose.